This invention concerns a rotary stepping motor for timepiece use comprising a core of magnetic material, a winding on said core, a stator magnetically coupled to said core and having two pole pieces separated or integrally formed with one another, a magnetized rotor encircled by said pole pieces exhibiting at least one pair of diametrally opposed poles, a gap separating the pole pieces from the rotor and magneto-mechanical means arranged and adapted to reverse the rotation sense of said rotor.
Micromotors equipped with magneto-mechanical means to reverse the rotation sense of a rotor are already known from the prior art.
Thus, German Pat. No. 1 006 806 describes a stepping motor provided with a U-formed bridle fixed to the stator. FIGS. 5 and 5a of this patent show that the arms of said bridle penetrate into a groove arranged in the soft iron poles of the rotor. Should the bridle be turned through 90.degree., the sense of rotation of the rotor will be reversed. In addition to the fact that this arrangement does not provide any means for adjusting the bridle, it will be understood that such will not be suitable for a watch stepping motor wherein the rotor is realized in a single piece with a circular magnet.
On the other hand, Swiss Pat. No. 613 349 discloses a watch steppping motor capable of rotation in two senses according to the position of a magnetic element pivotally mounted on one of the supports bearing the rotor. The construction proposed is awkward inasmuch as it requires considerable thickness and requires gear means should one wish to transform the rotational movement of the element into a longitudinal movement from a manual control stem.
The purpose of the present invention is to overcome these difficulties and thereby to propose means well adapted to a timepiece of small dimensions in order to reverse the rotation sense of its driving motor. Such means are set forth fully in the claims.